After showing off his amazing abs in a fringe crop top and neon green pants yesterday, the 27-year-old actor was spotted filming in Tybee Island on Tuesday in nothing but a nude-colored pair of undies.

With nothing but a strategically placed stuffed animal, Zac appears to be stranded on the beach, with the words "Team Hornet" written on his chest. In the film, Zac plays Robert De Niro's uptight grandson, who gets tricked into driving the perverted former Army general to Florida for spring break right before his own wedding.

And thanks to the not-so-secret set, now we know how Zac manages to look so buff on-screen -- the Neighbors actor was spotted doing push-ups in-between takes.